A land-based conundrum..

Post #19,730 by Ashton 11/29/01 3:42:38 PM Reply	A land-based conundrum.. I can't 'see' any further into the general problem than what's summarized above. Your more extensive analysis forced me to review what I (thought I) knew re cycle dynamics. I haven't retained most of the elegeant essays in (old, UK) mags like The Motor Cycle and Motorcycling - dunno if these mags even survive there, today (?) I used to subscribe to both. In US - ___ Jennings-like authors (believe he's a car-type guy) probably refined the earlier notions a bit, but I don't recall anything which "made cycle design er Simple" to grasp. Ex. Dick Mann, a notable track, scrambles all-around Ace some years back - was a friend of a cohort of mine. He was famous for pithy quips about such matters. One I recall re a Ceriani fancy fork assembly (with 28? different adjustments re rake, trail, fork damping etc. etc.) was in his style ~ Yeah and ya can get about (28!-1) screwed-up settings outta all that.. Let's go climb Snotty Hill and see.. Anyway, he designed frames, forks - raced them and sold them. Land stuff with the above er 'metastability' seems ~ about the inherent pseudo-balance of a cycle - esp. when sliding. Reminiscent of the cone as illustration of "degrees of freedom" in a geometry: Stable is on flat-end; conditional on side, where it can roll. And then we have the Famous Analogue of Windoze "stability": -- {{\\______/}} ___\\____/ ____\\__/ _____\\/____ ////////////// __ = a fly about to land Cycles are of course more stable than Windoze or - we'd all be dead. So omit the fly effect: there is a 'conditional stability' even in sliding-friction mode - until \ufffd happens to change abruptly (oil, leaves, gravel). Always amazing is - how fast! is the 'instinctive brain', especially in the Aces (whose boots I am unfit to run over). But that is not instantaneous, even amongst the mutants. What I cannot envision is - the 'way' that these behaviours can be translated to water! where "\ufffd" is as evanescent as.. integrity in a 100 mile radius of Redmond. What I mean is - this appears to be where the cycle model goes Nutzo. My guess - the folks engineering the Carter Copter most likely had similar fits in envisioning dynamics in YAN fluid: more so than mere water - and that had to include the lo-speed passages from ground to airborne, controlling of yaw, pitch etc. at near 0 ground (not rotor) speeds. I suspect that a lot of trial and error - mostly error would precede a rideable device (less'n one cheats and tosses in a gyro! with a Humongous MK\ufffd !) But maybe you're getting some stuff I'm not .. Happy sleuthing, Ashton
Post #19,751 by Ric Locke 11/29/01 8:32:00 PM Reply	Metastability is when it doesn't particularly want to go anywhere on its own, but if an external force intervenes -- Ash's fly, or (in the case of Windows) either trying to do something with it, or the simple passage of time... My version of the front ski was triangular from all directions -- long and skinny with the tip chopped off from the top, inverted isosceles from the front/back, and flat on top/deep aft from the side, for exactly the reasons Christian (who has plainly thought more deeply about it than I) gave. The back ski is roughly the same shape, but deeper to accommodate the water-jet's intake. Yes, the engine goes in the middle -- it's supposed to be a motorcycle analog! I simply thought that the engine lower unit of an outboard would be too much of a keel. We don't want to restrict the thing from sliding sideways! If we do, it's going over toward the outside of the turn, like a fatass freighter in ballast taking a turn too quickly, or an inept sailor weathering ship in a blow that's just a little too strong -- Therefore a water jet; engine properly between the knees, pump just under the saddle, ejecting the drive jet from the back. From a black-chrome trumpet :-) And Ashton, this thing is continually going to be in side-slide mode, more like a dirt-tracker busking dunes than anything on a highway. We need the crosswise flow to create a roll couple that holds it up when it leans. No winding in and out of cones here, especially at speed, and the turning radius will be ::ahem:: fairly large -- not that it matters. Motorcycles need a short turning radius so they can stay on the pavement, absent gravel patches (my elbows remember!) and spots of ice/grease/water. Our machine has the whole lake to skid in. As for fiberglass -- the frame should be made of tadaa welded tubing (Duh!), but the skis will be moderately complex shapes. Fiberglass (or carbon fiber composite) are the easiest way to do that, especially since it's possible to quick-and-dirty them on male armatures -- I strongly suspect there will be several iterations before the optimum shape emerges! Regards, Ric
Post #19,766 by Ashton 11/29/01 11:29:17 PM Reply	LRPD's eval: IWETHEY's Terrible Horde of Epithetic Yammerers (No doubt the Great Oracle approves of the Beastly refs.) OK - 'dirt track' I'd guess too; none o' that IOM precision dicing. So: since the shape has to somehow accomplish that which human lore + feedback does on land, umm where shall the skill enter in? T'would seem that, overcooking a 'turn' would result in merely.. increasing the turn radius automagically / not elbow burns (splashes?) But then.. I have little feel for What those folks do on water anyway - except with water skis it's apparent where the skill is needed, just to stay up. Played a bit with a speedboat at Tahoe once. Cute but tame, and seems to bring out the vandal-mind in most practitioners (and.. did I mention noisy?) Hmmm .. guess my Interest would be more in the vein of a video clip ~ 3 years back, about a (local!) guy developing a personal submarine! Lie prone in a tube; imagine an optically kewl paraboloid front. Don't recall max depth he was aiming for, but it was in hundreds of feet. Maybe even deeper. Alas, such a thing would be unlikely to reach prod. levels where anyone could afford it - but imagine an entire new world to explore, without the rigors of Tri-Mix and the usual SCUBA training and hazards. (Not to worry: exceed crush depth and.. no time to worry.) He seemed to think he could make a commercial one, though obviously not into the plan for usual bizness reasons. Physics + new materials - under $20K? Don't think I heard his hoped-for price. 3-D: now That's what a watercraft ought to do !! Ashton Beebe Verne
Post #19,771 by Andrew Grygus 11/30/01 12:24:16 AM Reply	Thought that was "Pathetic Yammerers" [link\|http://www.aaxnet.com\|AAx]
Post #19,781 by Silverlock 11/30/01 8:37:45 AM Reply	It is But see, since we are an eCommunity, we are ePathetic. And ePedantic. When I visit the aquarium, the same thought keeps running through my mind; Leemmmooonnn, Buuttteerrr, MMMmmmmmm good!
Post #19,816 by Ashton 11/30/01 4:28:57 PM Reply	LRPD be versatile as well as prescient.. empathic epithelial eclectic ecdysiastic ecoterroristic euphemistic eulogistic eutectic endo-European enneagrammatic eucharistic euphonious Euripidean expropriating extricating edifying excommunicating exasperating endodontic effusive ecStatic erroneous ectomorphic efficacious egregious eigenfunctioning extraterrestrial ejaculative (hey! that's about words) ejective emending ebullient eponymous and.. ecumenical (But only on Fridays) All Hail the Llanthropythical Elll Arrrrgh Pee Dee !!
Post #19,838 by Ric Locke 11/30/01 8:19:33 PM Reply	Where's the skill? OK - 'dirt track' I'd guess too; none o' that IOM precision dicing. So: since the shape has to somehow accomplish that which human lore + feedback does on land, umm where shall the skill enter in? T'would seem that, overcooking a 'turn' would result in merely.. increasing the turn radius automagically / not elbow burns (splashes?) Well, now, don't think even a Beowulf cluster (still current?) would be able to model the thing well enough to eliminate the skill. Too much lean? You get wet, with a strong flow up your nose (that is the direction it's going). Not enough, a-over-t -- call me skippy... And despite the utmost efforts of able engineers, the surface of the water is not a plane. Related story: A friend in high school once had a boat made of two pieces of marine plywood and a few sticks of 1x10. Build a wedge, 10" thick at the back, then cut the front out in a semicircle. Power was an old "seven-horse" Evinrude, from the days when outboard racing was by manufacturer's advertised horsepower. Change the reed and the jets, and it was more like fifteen. Directional "control" was the skeg of a broken slalom ski, screwed to the bottom in more or less the center... we were out on the lake one day, with plenty of fuel, and another friend was driving it. Probably thirty MPH across the water -- and a Chris-Craft passed across his bows at about ten knots. Have you ever seen the bow wave one of those puppies puts out? Boat climbed the wave, went airborne, then (against all expectation) began nosing over instead of flipping bow-up. Thin end of wedge entered the other bow wave, more or less perpendicular to the water surface. plurg! Hardly a splash. Tim had on a good life preserver, as evidenced by the fact that he did bob to the surface eventually, as did the boat (though quite a ways away from the, er, scene of the incident). Don't think the nabobs in the Love Boat ever noticed anything... The boat was retired to pontoon duty on our fishing trips. Ah, youth. Regards, Ric

Welcome to IWETHEY!